Protractor.



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PROTRAC'TOR.

SPECIFICATION' forming part of Letters Patent No. 655,848, dated August 14, 1900. Application iiled March 28, 1900. Serial No. 10,498. {No model.)

To au whom t may conceive:

Be it known that LWINFIELD S. CARHART, a citizen of the United States, residing at Telluride, in the county of San Miguel and State of Colorado, have invented certain new and useful Improvements in Protractors; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to improvements in protractors, and is adapted to be used as an attachment for transits such as are commonly used by civil engineers.

It comprises a rod having hollow arms and rods adapted to extend into the hollow arms, the said rods having needle-points and means for adjusting them in the hollow rods and means for attaching the instrument to a transit, whereby it may be used upon a drawing-board or plotting-table.

It also consists in certain other constructions,combinations,and arrangementofparts, as will be hereinafter fully described and specically claimed.

Figure 1 in the accompanying drawings represents a side elevation of a protractor made in accordance with my invention and applied to an engineers transit. Fig. 2 represents an enlarged detail vertical section through the clamping-ring and the end of the protractor attachment secured thereto. Fig. 3 Y

represents a detailsectional view through the end of the protractor attachment, a portion of the attaching means being shown in elevation. Fig. 4 represents a detail View of the clamping-band separated from the protractor attachment. v

My improved protractor is designed to be used upon plotting-tables in connection with a transit or other similar instrument having a compass and Vernier-plates,whereby angles can be accurately ascertained, the protractor being attached to suchinstrument and being thereby moved to the desired angle, so that a line or linesmay be drawn in accordance therewith. v.

The protractor consists of a rod or bar, as l, which is preferably enlarged at one end, as at 2, and provided with a clampingband 3. The said band 3 is preferably pivotally secured to the enlarged end 2 of the bar 1 by means of `a screw, as 13, ou one side of its periphery'and upon the other side thereof is adjustably secured tothe said band by means of a setserew 14, which passes through a slot formed in a projection l5 on the said enlarged end 2. The said screw 14 engages a screw-threaded hole 16 in the band 3. The screw 14 is not tightened until the band 3 has been secured in place onthe telescope, thus permitting of theexpansion and contraction of the said band without being hampered by the enlarged end of the protractor attachment. After the band has been tightened the set-screw 14 may be tightened for rigidly holding the arm 1 in place. The band 3 is adapted to be tightened or loosened by means of a set-screw, as 4, so that it can be secured to the telescope of a transit or other similar instrument. The clamping-band and screw also make it possible to apply the instrument to telescopes of different sizes. The rod 1 is provided with two or more depending arms, as 5 5, which are hollow and which together with the rod 1 are preferably formed of some light materal, such as aluminium.

Telescoping into the arms 5 5 are rods 6 6, which are provided with needle-points, as 7, at their outer ends. Their inner ends are adapted to slide in the hollow arms 5 5 and may be clamped in adjusted positions in the said arms by means of set-screws, as 8 8, the said set-screws passing through slots 9,formed in the hollowarms 5. By this adjustment the points 7 7 may be brought into proper relation to the surface of a drawing or plotting table, as 10, and may be adjusted for use with transits or other .instruments of different heights.

In using a protractor of this character a transit or other su rveyors instrument having a compass is preferably removed from its tripod and placed upon the plotting-table, so that its compass is horizontal. The protractor is then clamped upon the end of the telescope, as seen in the drawings, and the rods G G are adjusted in the hollow arms 5, so as to bring their points 7 7 in contact with the surface of the plotting-table 10. By the use of the compass on the transit and the Vernierplates different angles can be accurately laid down, lines being drawn through the points IOO indicated by the needle-points of the protractor.

It will be readily seen that an instrument of this character can be used to ascertain the slightest variations in the running el' lines upon different angles, as is very desirable in engineers or surveyors work. An attachment of this kindalso may be used with any transit, level, or other surveyors instrument having a compass or other means for ascertaining angles. The article is also exceedingly simple in construction and may be made in an inexpensive manner.

AHaving thus described my invention, what I claim as new, and desire to secure by Letters Patent, is-

l. A protractor attachment comprising a rod or bar having depending arms, rods extending into the said arms, and means for holding them in their adjusted positions, and means for securing the rod or bar to an instrument for ascertaining angles.

2. Aprotractor attachment comprisinga rod or bar having depending hollow arms, rods moving in the said hollow arms, set-screws for adjustably securing the rods at different heights in the said arms, the said set-screws passing through slots in the arms, needlepoints formed upon the said rods, and a clampin g-band for securing the protractor to an instrument for ascertaining angles.

3. An attachment for surveyors7 or engi- 'neers instruments comprising a bar having depending hollow arms, a clamping-band for attaching the bar to the telescope of a surveyors transit or other similar instrument, rods adapted to be adjusted in the hollow arms, set-screws passing through slots in the said arms for securing the rods in their different adj usted positions, the construction being such that by attaching the device to the telescope of a transit it may be used as a protractor upon a plotting table or drawingboard for laying out different angles, substantially as described.

In testimony whereof I hereunto afx my signature in presence of two witnesses.

WINFIELD S. CARHART.

Witnesses:

W. R. BEATTIE, W. ROBINSON. 

